384 Dr. A. LI. Hughes on the 



Mercuric Chloride. 



Leak. 



f First 60 sees. ] =<-6 



First exposures . . \ Next 120 „ v 4*5 



I Next 120 „ J 8-0 



Exposed 3 mins 14*5 



Exposed 30 „ 88*0 



In dark 19 hrs 144'0 



Exposed 5 mins 100*0 



Exposed 40 „ 122-0 



Bismuth Trichloride. 



Leak. 



First exposure = 10*7 



Exposed 2 mins , . . 20 



Exposed 5 „ 45 



Jn dark 8 „ 49 



Exposed 8 „ 62 



Exposed 20 „ 93 



It will be noticed that, generally speaking, the effect ot 

 keeping the surface in the dark is to reduce the leak at the 

 next exposure, or, i£ this be not effected, to reduce the rate 

 at which the leak increases. 



Antimony Tri-iodide. 

 This salt differed from the others in that it started with a 

 big leak, and that prolonged exposure to light caused a reduc- 

 tion in this leak. 



Leak. 



First exposure = 110 



Exposed 6 mins 143 



Exposed 14 „ 80 



Exposed 20 ,, 55 



In dark 90 „ 82 



Lead Iodide. 

 No leak was obtained from lead iodide in the first ex- 

 periments. The results o£ long exposure to light with the 

 other salts suggested a further investigation of the effect o£ 

 prolonged exposure on lead iodide. 



Leak. 



First exposure = <*2 



Exposed 3 mins 2*8 



Exposed 5 „ 4*5 



Exposed 40 „ 12'7 



Exposed 70 „ 16-2 



The effect with lead iodide is much smaller than with the 

 other salts and requires a longer exposure to produce it. 



